The ParserFunctions extension provides eleven additional parser functions to supplement the "magic words", which are already present in MediaWiki. (It may be configured to provide additional parser functions for string handling; these string functions are documented elsewhere.) All the parser functions provided by this extension take the form:

This function evaluates a mathematical expression and returns the calculated value. This function is also available in Scribunto via the mw.ext.ParserFunctions.expr function.

{{#expr: expression }}

The available operators are listed to the right, in order of precedence. See Help:Calculation for more details of the function of each operator. The accuracy and format of the result returned will vary depending on the operating system of the server running the wiki and the number format of the site language.

When evaluating using boolean algebra, zero evaluates to false, and any nonzero value, positive or negative, evaluates to true:

{{#expr: 1 and -1 }} → 1

{{#expr: 1 and 0 }} → 0

{{#expr: 1 or -1 }} → 1

{{#expr: -1 or 0 }} → 1

{{#expr: 0 or 0 }} → 0

An empty input expression returns an empty string. Invalid expressions return one of several error messages, which can be caught using the #iferror function:

{{#expr: }} →

{{#expr: 1+ }} → Expression error: Missing operand for +.

{{#expr: 1 = }} → Expression error: Missing operand for =.

{{#expr: 1 foo 2 }} → Expression error: Unrecognized word "foo".

The order of addition and subtraction operands before or after a number is meaningful and may be treated as a positive or negative value instead of as an operand with an erroneous input:

{{#expr: +1 }} → 1

{{#expr: -1 }} → -1

{{#expr: + 1 }} → 1

{{#expr: - 1 }} → -1

Note, if using the output of magic words, you must raw-format them in order to remove commas and translate the numerals. For example, {{NUMBEROFUSERS}} results in 8.281.631, where we want 8281631, which can be obtained using {{formatnum:{{NUMBEROFUSERS}}|R}}. This is especially important in some languages, where numerals are translated. For example, in Bengali, {{NUMBEROFUSERS}} produces ৩০,০৬১.

{{#expr:{{NUMBEROFUSERS}}+100}} → 108.281

{{#expr:{{formatnum:{{NUMBEROFUSERS}}|R}}+100}} → 8281731

Warning:

The operator mod gives wrong results for some values of the second argument:

If you want to do calculations based on dates (ex. test whether current date and time is after some other date and time), first convert the time to number of seconds after January 1, 1970 using {{#time: xNU }}, then you can simply add and subtract dates as numbers.

Op- an Ofronnen

Rounds off the number on the left to a multiple of 1/10 raised to a power, with the exponent equal to the truncated value of the number given on the right.

To round up or down use unary ceil or floor respectively.

Test case

Resultat

Method of rounding

{{#expr: 1/3 round 5 }}

0.33333

Final digit is < 5, so no apparent rounding occurs

{{#expr: 1/6 round 5 }}

0.16667

Final digit is ≥ 5, so it is rounded up

{{#expr: 8.99999/9 round 5 }}

1

Again, the result is rounded up on the last digit, which results in additional rounding

{{#expr: 1234.5678 round -2 }}

1200

Rounded to nearest 100 because negative values round to the left of the decimal point

{{#expr: 1234.5678 round 2 }}

1234.57

Rounded to nearest 100th because positive values round to the right of the decimal point

{{#expr: 1234.5678 round 2.3 }}

1234.57

Decimals in the rounding index make no difference in the rounded result

{{#expr: trunc 1234.5678 }}

1234

Decimal portion truncated (chopped off)

Rounding to the nearest integer

{{#expr: 1/3 round 0 }}

0

Down to the nearest integer, which is zero

{{#expr: 1/2 round 0 }}

1

Up to the nearest integer, which is one

{{#expr: 3/4 round 0 }}

1

Up to the nearest integer, which is one

{{#expr: -1/3 round 0 }}

0

Up to the nearest integer, which is zero

{{#expr: -1/2 round 0 }}

-1

Down to the nearest integer, which is negative one

{{#expr: -3/4 round 0 }}

-1

Down to the nearest integer, which is negative one

Rounding up or down with ceil and floor

{{#expr: ceil(1/3) }}

1

Up to the next larger integer, which is one

{{#expr: floor(1/3) }}

0

Down to the next smaller integer, which is zero

{{#expr: ceil(-1/3) }}

0

Up to the next larger integer, which is zero

{{#expr: floor(-1/3) }}

-1

Down to the next smaller integer, which is negative one

{{#expr: ceil 1/3 }}

0.33333333333333

Not rounded, since 1 already is an integer

Warning:

Interpreted as (ceil 1)/3, not ceil(1/3), as you might expect

Strings

Expressions only work with number-like values, they cannot compare strings or characters. #ifeq can be used instead.

This function first tests whether the first parameter is not empty. If the first parameter is not empty the function displays the second argument. If the first parameter is empty or contains only whitespace characters (spaces, newlines, etc.) it displays the third argument.

{{#if: | yes | no}} → no

{{#if: string | yes | no}} → yes

{{#if: | yes | no}} → no

{{#if:

| yes | no}} → no

The test string is always interpreted as pure text, so mathematical expressions are not evaluated:

{{#if: 1==2 | yes | no }} → yes

{{#if: 0 | yes | no }} → yes

The last parameter (false) may be omitted:

{{#if: foo | yes }} → yes

{{#if: | yes }} →

{{#if: foo | | no}} →

The function may be nested. To do so, nest the inner #if function in its full form in place of a parameter of the enclosing #if function. Up to seven levels of nesting is possible, although that may depend on the wiki or a memory limit.

If the strings to be compared are given as equal calls to the same template containing such tags, then the condition is true, but in the case of two templates with identical content containing such tags it is false.

Warning:

Be careful when comparing against the current page title using the page name magic words. These magic words convert special characters into numeric HTML entities. This may result in misleading results. For example, if you are on a page titled "L'Aquila"...

NOTE: The above is actually wrong: Due to improvements, it will now return "equal". However, this can be important in some other cases; for example, {{FULLPAGENAME}}, depending on wiki, may capitalize the first letter, and will replace all underscores with spaces.

#iferror

This function takes an input string and returns one of two results; the function evaluates to true if the input string contains an HTML object with class="error", as generated by other parser functions such as #expr, #time and #rel2abs, template errors such as loops and recursions, and other "failsoft" parser errors.

{{#iferror: test string | value if error | value if correct }}

One or both of the return strings can be omitted. If the correct string is omitted, the test string is returned if it is not erroneous. If the error string is also omitted, an empty string is returned on an error:

except for an empty or wrong input expression (an error message is treated as an empty string; it is not equal to zero, so we get value if true).

{{#ifexpr: = | yes | no }} → Expression error: Unexpected = operator.

vergläichen

{{#ifeq: {{#expr: = }} | 0 | no | yes }} → yes

Either or both the return values may be omitted; no output is given when the appropriate branch is left empty:

{{#ifexpr: 1 > 0 | yes }} → yes

{{#ifexpr: 1 < 0 | yes }} →

{{#ifexpr: 0 = 0 | yes }} → yes

{{#ifexpr: 1 > 0 | | no}} →

{{#ifexpr: 1 < 0 | | no}} → no

{{#ifexpr: 1 > 0 }} →

#ifexist

This function takes an input string, interprets it as a page title, and returns one of two values depending on whether or not the page exists on the local wiki.

{{#ifexist: page title | value if exists | value if doesn't exist }}

The function evaluates to true if the page exists, whether it contains content, is visibly blank (contains meta-data such as category links or magic words, but no visible content), is blank, or is a redirect. Only pages that are redlinked evaluate to false, including if the page used to exist but has been deleted.

If a page checks a target using #ifexist:, then that page will appear in the Special:WhatLinksHere list for the target page. So if the code {{#ifexist:Foo}} were included live on this page (Help:Extension:ParserFunctions/lb), Special:WhatLinksHere/Foo will list Help:Extension:ParserFunctions/lb.

On wikis using a shared media repository, #ifexist: can be used to check if a file has been uploaded to the repository but not to the wiki itself:

If a local description page has been created for the file, the result is exists for all of the above.

#ifexist: does not work with interwiki links.

ifexist limits

#ifexist: is considered an "expensive parser function"; only a limited number of which can be included on any one page (including functions inside transcluded templates). When this limit is exceeded, any further #ifexist: functions automatically return false, whether the target page exists or not, and the page is categorized into Category:Pages with too many expensive parser function calls. The name of the tracking category may vary depending on the content language of your wiki.

For some use cases it is possible to emulate the ifexist effect with css, by using the selectors a.new (to select links to unexisting pages) or a:not(.new) (to select links to existing pages). Furthermore, since the number of expensive parser functions that can be used on a single page is controlled by $wgExpensiveParserFunctionLimitManual:$wgExpensiveParserFunctionLimit, one can also increase the limit in LocalSettings.php if needed.

#rel2abs

This function converts a relative file path into an absolute filepath.

{{#rel2abs: path }}

{{#rel2abs: path | base path }}

Within the path input, the following syntax is valid:

. → the current level

.. → "go up one level"

/foo → "go down one level into the subdirectory /foo"

If the base path is not specified, the full page name of the page will be used instead:

{{#rel2abs: /quok | Help:Foo/bar/baz }} → Help:Foo/bar/baz/quok

{{#rel2abs: ./quok | Help:Foo/bar/baz }} → Help:Foo/bar/baz/quok

{{#rel2abs: ../quok | Help:Foo/bar/baz }} → Help:Foo/bar/quok

{{#rel2abs: ../. | Help:Foo/bar/baz }} → Help:Foo/bar

Invalid syntax, such as /. or /./, is ignored. Since no more than two consecutive full stops are permitted, sequences such as these can be used to separate successive statements:

Output the full month name in the genitive form for site languages that distinguish between genitive and nominative forms. This option is useful for many Slavic languages like Polish, Russian, Belarusian, Czech, Slovak, Slovene, Ukrainian, etc.

For Polish:

(nominative)

{{#time:d F Y|20 June 2010|pl}} → 20 czerwiec 2010

(genitive)

{{#time:d xg Y|20 June 2010|pl}} → 20 czerwca 2010

Woch

W

ISO 8601 week number, zero-padded.

49

Dag

j

Day of the month, not zero-padded.

9

d

Day of the month, zero-padded.

09

z

Day of the year (January 1 = 0).Note: To get the ISO day of the year add 1.

Like xn, but as a toggled flag, which endures until the end of the string or until the next appearance of xN in the string.

xr

Format the next number as a roman numeral. Only works for numbers up to 10,000(upto 3,000 in pre MediaWiki 1.20).

{{#time:xrY}} → MMXVI

xh

Format the next number as a Hebrew numeral.

{{#time:xhY}} → ב'ט"ז

This parser function takes a date and/or time (in the Gregorian calendar) and formats it according to the syntax given. A date/time object can be specified; the default is the value of the magic word{{CURRENTTIMESTAMP}} – that is, the time the page was last rendered into HTML.

{{#time: format string }}

{{#time: format string | date/time object }}

{{#time: format string | date/time object | language code }}

The list of accepted formatting codes is given in the table to the right. Any character in the formatting string that is not recognized is passed through unaltered; this applies also to blank spaces (the system does not need them for interpreting the codes). There are also two ways to escape characters within the formatting string:

A backslash followed by a formatting character is interpreted as a single literal character

Characters enclosed in double quotes are considered literal characters, and the quotes are removed.

The range of acceptable input is 1 January 0111 → 31 December 9999. For the years 100 through 110 the output is inconsistent, Y and leap years are like the years 100-110, r, D, l and U are like interpreting these years as 2000-2010.

The weekday is supplied for the years 100-110 and from 1753, for the years 111-1752 the r-output shows "Unknown" and the l-output "<>". As a consequence, the r-output is not accepted as input for these years.

Full or partial absolute dates can be specified; the function will "fill in" parts of the date that are not specified using the current values:

{{#time: Y | January 1 }} → 2016

Warning:

The fill-in feature is not consistent; some parts are filled in using the current values, others are not:

{{#time: Y m d H:i:s | June }} → 2016 06 09 00:00:00 Gives the start of the day, but the current day of the month and the current year.

{{#time: Y m d H:i:s | 2003 }} → 2003 12 09 00:00:00 Gives the start of the day, but the current day of the year.

A six-digit number is interpreted as hours, minutes and seconds if possible, but otherwise as an error (not, for instance, a year and month):{{#time: Y m d H:i:s | 195909 }} → 2016 12 09 19:59:09 Input is treated as a time rather than a year+month code.{{#time: Y m d H:i:s | 196009 }} → Error: Invalid time.Although 19:60:09 is not a valid time, 196009 is not interpreted as September 1960.

The function performs a certain amount of date mathematics:

{{#time: d F Y | January 0 2008 }} → 31 Dezember 2007

{{#time: d F | January 32 }} → Error: Invalid time.

{{#time: d F | February 29 2008 }} → 29 Februar

{{#time: d F | February 29 2007 }} → 01 Mäerz

{{#time:Y-F|now -1 months}} → 2016-November

The total length of the format strings of the calls of #time is limited to 6000 characters[1].

Time Zone issue

There is a bug in this #time parser function (more specifically in PHP DateTime) that does not allow the passing-in of non-integers as relative time zone offsets. This issue does not apply when using an on-the-hour time zone, such as EDT. For example:

{{#time:g:i A | -4 hours }} ==> 11:24 AM

However, Venezuela is on a -4.5 hours time offset from UTC, and thus using its time zone will not normally allow the correct calculation of a relative time zone offset. Here's what happens:

{{#time:g:i A | -4.5 hours }} ==> 12:24 AM

To workaround this issue, simply convert the time into minutes or seconds, like this:

{{#time:g:i A | -270 minutes }} ==> 10:54 AM

{{#time:g:i A | -16200 seconds }} ==> 10:54 AM

(Tim Starling, the developer of this function, provided the exact syntax for this solution.)

#timel

This function is identical to {{#time: ... }}, except that it uses the local time of the wiki (as set in $wgLocaltimezone) when no date is given.

{{#time: Y-m-d }} → 2016-12-09

{{#timel: Y-m-d }} → 2016-12-09

{{#time: Y F d H:i:s}} → 2016 Dezember 09 15:24:16

{{#timel: Y F d H:i:s}} → 2016 Dezember 09 15:24:16

#titleparts

This function separates a page title into segments based on slashes, then returns some of those segments as output.

{{#titleparts: pagename | number of segments to return | first segment to return }}

If the number of segments to return parameter is not specified, it defaults to "0", which returns all the segments from the first segment to return (included). If the first segment to return parameter is not specified or is "0", it defaults to "1":

Negative values are accepted for both values. Negative values for the number of segments to return parameter effectively 'strips' segments from the end of the string. Negative values for the first segment to return translates to "start with this segment counting from the right":

{{#titleparts: Talk:Foo/bar/baz/quok | -1 }} → Talk:Foo/bar/bazStrips one segment from the end of the string. See also {{BASEPAGENAME}}.

{{#titleparts: Talk:Foo/bar/baz/quok | -4 }} → Strips all 4 segments from the end of the string

{{#titleparts: Talk:Foo/bar/baz/quok | -5 }} → Strips 5 segments from the end of the string (more than exist)

{{#titleparts: Talk:Foo/bar/baz/quok | -1 | 2 }} → bar/bazStrips one segment from the end of the string, then returns the second segment and beyond

{{#titleparts: Talk:Foo/bar/baz/quok | -1 | -2 }} → bazStart copying at the second last element; strip one segment from the end of the string

Before processing, the pagename parameter is HTML-decoded: if it contains some standard HTML character entities, they will be converted to plain characters (internally encoded with UTF-8, i.e. the same encoding as in the MediaWiki source page using this parser function).

For example, any occurence of &quot;, &#34;, or &#x22; in pagename will be replaced by ".

No other conversion from HTML to plain text is performed, so HTML tags are left intact at this initial step even if they are invalid in page titles.

Some magic keywords or parser functions of MediaWiki (such as {{PAGENAMEHelp:Magic words#Page names}} and similar) are known to return strings that are needlessly HTML-encoded, even if their own input parameter was not HTML-encoded:

The titleparts parser function can then be used as a workaround, to convert these returned strings so that they can be processed correctly by some other parser functions also taking a page name in parameter (such as {{PAGESINCAT:Help:Magic words#PAGESINCAT}} but which are still not working properly with HTML-encoded input strings.

The string is split a maximum of 25 times; further slashes are ignored and the 25th element will contain the rest of the string. The string is also limited to 255 characters, as it is treated as a page title:

{{#titleparts: [[page]]/123 | 1 | 2 }} → page/123. Does not work because brackets are illegal in page titles and this parser function does not process links embedded in its input pagename parameter, even when they use the MediaWiki syntax, or any other HTML or MediaWiki tags.

{{#titleparts: red/#00FF00/blue | 1 | 3 }} → "". Does not work because "#" is also illegal in page titles.

Warning:

This function does not degrade gracefully if your input exceeds 255 characters. If the inputted string is 256 characters long or more, this function will simply toss the string back at you.

General points

Substitution

Parser functions can be substituted by prefixing the hash character with subst::

{{subst:#ifexist: Help:Extension:ParserFunctions/lb | [[Help:Extension:ParserFunctions/lb]] | Help:Extension:ParserFunctions/lb }} → the code [[Help:Extension:ParserFunctions/lb]] will be inserted in the wikitext since the page Help:Extension:ParserFunctions/lb exists.

Warning:

The results of substituted parser functions are undefined if the expressions contain unsubstituted volatile code such as variables or other parser functions. For consistent results, all the volatile code in the expression to be evaluated must be substituted. See Help:Substitution.

Redirects

Escaping pipe characters in tables

Parser functions will mangle wikitable syntax and pipe characters (|), treating all the raw pipe characters as parameter dividers. To avoid this, most wikis used a template Template:! with its contents only a raw pipe character (|), since MW 1.24 a {{!}} magic word replaced this kludge. This 'hides' the pipe from the MediaWiki parser, ensuring that it is not considered until after all the templates and variables on a page have been expanded. It will then be interpreted as a table row or column separator. Alternatively, raw HTML table syntax can be used, although this is less intuitive and more error-prone.

You can also escape the pipe character for display as a plain, uninterpreted character using an HTML entity: &#124; .

Description

You type

You get

Escaping pipe character as table row/column separator

{{!}}

|

Escaping pipe character as a plain character

&#124;

|

Stripping whitespace

Whitespace, including newlines, tabs, and spaces, is stripped from the beginning and end of all the parameters of these parser functions. If this is not desirable, comparison of strings can be done after putting them in quotation marks.

{{#ifeq: foo | foo | equal | not equal }} → equal

{{#ifeq: "foo " | " foo" | equal | not equal }} → not equal

To prevent the trimming of then and else parts, see m:Template:If. Some people achieve this by using <nowiki> </nowiki> instead of spaces.

foo{{#if:|| bar }}foo → foobarfoo

foo{{#if:||<nowiki></nowiki> bar <nowiki></nowiki>}}foo → foo bar foo

However, this method can be used to render a single whitespace character only, since the parser squeezes multiple whitespace characters in a row into one.

In this example, the white-space: pre style is used to force the whitespace to be preserved by the browser, but even with it the spaces are not shown. This happens because the spaces are stripped by the software, before being sent to the browser.

It is possible to workaround this behavior replacing whitespaces with &#32; (breakable space) or &nbsp; (non-breakable space), since they are not modified by the software: